Effect of High Temperature Curing on the Frost Resistance of Recycled Aggregate Concrete and the Physical Properties of Second-Generation Recycled Coarse Aggregate under Freeze-Thaw Cycles

Abstract

With the emphasis on environmental issues, the recycling of waste concrete, even recycled concrete, has become a hot spot in the field of architecture. But the repeated recycling of waste concrete used in harsh environments is still a complex problem. This paper discusses the durability and recyclability of recycled aggregate concrete (RAC) as a prefabricated material in the harsh environment, the effect of high-temperature curing (60°C, 80°C, and 100°C) on the frost resistance of RAC and physical properties of the second generation recycled coarse aggregate (RCA₂) of RAC after 300 freeze-thaw cycles were studied. The frost resistance of RAC was characterized by compressive strength, relative dynamic elastic modulus, and mass loss. As the physical properties of RCA₂, the apparent density, water absorption, and crushing value were measured. And the SEM images of RAC after 300 freeze-thaw cycles were shown. The results indicated that the frost resistance of RAC cured at 80°C for 7 days was comparable to that cured in the standard condition (cured for 28 days at 20°C ± 2°C and 95% humidity), and the RAC cured at 100°C was slightly worse. However, the frost resistance of RAC cured at 60°C deteriorated seriously. The RAC cured at 80°C for 7 days is the best. Whether after the freeze-thaw cycle or not, the RCA that curd at 60°C, 80°C, and 100°C for 7 days can also meet the requirements of Grade III RCA and be used as the aggregate of non-bearing part of prefabricated concrete components. RCA₂ which is cured at 80°C for 7 days had the best physical properties.